Browse Prior Art Database

10 MHz Ultrasonic Silicon Cleaning Tool

IP.com Disclosure Number: IPCOM000112781D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Koretsky, RG: AUTHOR [+3]

Abstract

This device is designed to clean fully fabricated silicon wafers.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 98% of the total text.

10 MHz Ultrasonic Silicon Cleaning Tool

      This device is designed to clean fully fabricated silicon
wafers.

      As shown in the Figure, a tank containing pure water with a
gently circulating flow is used into which the wafer is submerged.
The wafer is placed in a holder on a reciprocating arm that moves the
sample in a vertical plane.  One or more 10 MHz focussed acoustic
transducers are positioned so that the focused beam impinges on the
Si, as shown.  The ultrasonic energy is used here to remove debris
from the wafer.  The flow system provides a means for removing any
loosened debris.  Transducers are presently available which can
deliver on the order of 1X1000 W/cm2  in the focal plane.  At 10 MHz
this is approximately 2 orders of magnitude below which cavitation
occurs (*).  Cavitation can result in very large random shock waves,
potentially damaging to the wafers being cleaned.  However, by going
to high frequencies and focusing the acoustic energy, a large
controlled energy density is available without the damaging, random
fluctuations.  At typical frequencies used for ultrasonic cleaners,
i.e., in the 10 KHz range, 1 W/cm2  is sufficient to cause
cavitation, a phenomenon that our device circumvents by going to the
higher frequencies.  Thus, our device can deliver a large amount of
acoustic energy for cleaning without resorting to cavitation.

Reference

(*)  M. P. Drake, "Electrodeposition in Ultrasonic Fields," Trans.
   Inst.  of Metal F...